Human placental estradiol 17 beta-dehydrogenase has been purified and crystallized and attempts are being made to grow crystals large enough to allow structural studies X-ray crystalography and compare these with results obtained using affinity-labeling steroids. Structural studies on chick ovuduct progesterone receptor and calf uterine estradiol receptor will be carried out using affinity-labeling steroids. Efforts to stablize and purify this small amount of estradiol 17 Beta-dehydrogenase in horse placenta will be carried out this up-coming year.